1. Field of the Invention
This invention relates in general to antenna systems, and in particular to an integrated dual beam reflector antenna.
2. Description of the Related Art
Communications satellites have become commonplace for use in many types of communications services, e.g., data transfer, voice communications, television spot beam coverage, and other data transfer applications. As such, satellites must provide signals to various geographic locations on the Earth""s surface. As such, typical satellites use customized antenna designs to provide signal coverage for a particular country or geographic area.
Satellites are typically required to generate multiple beams to provide multiple or overlapping geographical areas with communications signals. Typically, satellites use multiple antennas or a shaped reflector antenna to provide the multiple beams required. Shaped reflector antennas can be optimized for a given shaped beam, but it is desirable to generate multiple beams from a single shaped surface for ease of mechanical packaging. The single shaped surface, however, has a degraded performance with respect to multiple shaped reflector surfaces, which is the main reason for using multiple shaped reflectors to generate multiple coverage beams. By having multiple shaped reflector surfaces, severe demands are made on the spacecraft with reference to mechanical packaging.
A related approach is to use a major portion of the reflector surface for a primary beam, and a smaller portion of the reflector surface is illuminated for auxiliary beams such as tracking beams, spacecraft command and control, a communication beam, etc. However, such configurations lead to interaction between the auxiliary reflector surface and the primary feed horns.
It can be seen, then, that there is a need in the art for antenna systems that can provide multiple beams from a single reflector surface. It can also be seen that there is a need in the art for single reflector surfaces that reduce the interaction between the reflector surface and the feed horns. It can also be seen that there is a need in the art for single reflector surfaces that have increased performance for multiple beam applications.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a method for generating multiple antenna beams and a system for generating multiple antenna beams. The system comprises a first reflector surface that has a primary and at least a first auxiliary surface, and a second reflector surface, and also comprises first, second, and third feed horns. The first reflector surface and the second reflector surface may share a common axis of symmetry. The first feed horn illuminates the primary surface with radio frequency (RF) energy, the second feed horn illuminates the auxiliary surface with RF energy, and the third feed horn illuminates the second reflector surface with RF energy. The first feed horn and third feed horn are removed from an axis of symmetry of the auxiliary surface.
The method comprises illuminating a primary portion of a first reflector surface with RF energy from a first feed horn, illuminating an auxiliary portion of the first reflector surface with RF energy from a second feed horn, illuminating a second reflector surface with RF energy from a third feed horn, wherein the first feed horn and third feed horn are removed from an axis of symmetry of the auxiliary portion of the first reflector surface.
The present invention provides an antenna system that can provide multiple beams from a single reflector surface. The present invention also provides single reflector surfaces that reduce the interaction between the reflector surface and the feed horns. The present invention also provides single reflector surfaces that have increased performance for multiple beam applications.